In a broach pulley tool an axially displaceable spindle grasps the end region of a broach and pulls the broach through the workpiece to remove metal. Keyways, splines and other configurations are often formed in the bore of workpieces by broach pullers.
Some workpieces, such as the gearing used in transmissions, requires an internal spiral spline and such helical splines can be formed by broach pulling machine tools by rotating the spindle and tool as the tool is axially displaced. In such instances rotational orientation is often required between the configuration of the workpiece bore and other configurations defined on the workpiece, such as gear teeth defined on the workpiece periphery.
The connection between the operating spindle and the broach tool is usually by the use of jaws carried by the spindle engaging an annular recess within the tool end region. The jaws engage an oblique surface defining the edge of the recess nearest the broach end, and while the jaws are able to impose sufficient axial force on the tool to provide cutting, the axial dimension of the jaws is less than that of the recess and an axial lost motion between the tool and spindle occurs. This lost motion or clearance between the spindle and tool, even though the tool is keyed to prevent relative rotation with respect to the spindle, results in inaccuracies occurring between the resultant cut and the desired location of the cut on the workpiece. Such inaccuracies are particularly significant when utilizing a helical broach as the spindle and broach are rotated during cutting, and with previous broaching equipment it is necessary to compensate for this problem by locating the workpiece relative to the tool in a predetermined manner, or by other less than desired procedures.
A number of devices have been used to interconnect broaches and spindles as shown in U.S. Pat. Nos. 1,984,104; 2,135,157; 2,135,861; 3,199,409; 4,180,360 and 4,266,894. However, none of these devices are capable of removing the inaccuracies and lost motion presently attendant with broaching tools, particularly rotary helical broaching tools.
It is an object of the invention to provide a helical broach puller which eliminates axial lost motion and play between the pulling spindle and broaching tool.
It is another object of the invention to provide a helical broach puller utilizing spindle mounted radially displaced jaws engagable with an annular recess within the broach end region wherein radial jaw displacement prevents relative axial movement between the spindle and broaching tool.
An additional object of the invention is to provide a broach puller having jaws engagable with the broach at spaced axial positions wherein the jaws are operated by a common actuator and are sequentially actuated.
Yet a further object of the invention is to provide a broach puller utilizing axially spaced jaws for engaging the broach at axially spaced locations to eliminate relative axial displacement between the spindle and broach and wherein positive metal-to-metal locking relationships between the jaws and broach is achieved.
A broach of the type utilized with the concept of the invention includes a cylindrical end region having a recess defined therein wherein the recess configuration includes oblique shoulders. In the usual construction the broach machine tool includes a rotatable spindle having a socket receiving the broach tool end region and radially movable jaws defined in the spindle engage the tool recess shoulder closest to the tool end for interconnecting the spindle and tool and permitting an axial pulling force to be applied to the tool. The radial position of the jaw is determined by an axially displaceable cam.
In accord with the invention a second set of radially movable jaws is defined upon the spindle axially displaced from the first set of jaws and in alignment with the tool recess shoulder not engaged by the first jaw set. The second set of jaws produces an axial force on the tool in an opposite direction to the axial force imposed on the tool by the first jaw set. Thus, engagement of both sets of jaws with opposite sides of the tool recess eliminates any play, clearance or lost motion between the spindle and tool in the axial direction. This relationship permits both the axial and rotative relationship of the spindle and tool to be accurately controlled and determined, overcoming previous alignments and orientation problems.
Both sets of jaws are operated by an annular cam sleeve axially displaceable on the spindle. Compression springs bias the cam sleeve in the direction inwardly radially displacing the jaw sets, while a sleeve abutment is engaged during spindle displacement in a non-broaching direction to compress the sleeve springs and permit retraction of the jaw sets for removal of the tool from the spindle socket.